Fluid cooling system



mim cooLI-NG SYSTEM Filed Dec. 23, 1957 H. R. CRAG K 2,168,157

svsheetsrsneet 1 I hveto. Y Y Harry Crago,

' His AttoYT-gey.

H. R. CRAGO FLUID COOLINGA SYSTEM Fi'l edADec. 23, 1937 3 Sheets-Sheet 2Figi..

. IhveY-VGOY:

` Harry R. C ago by VW $MMW` a l-Hs Attorney.

Aug. 1, 19.39. H; R. cRAGo 2,153,157

FLUID COOLING sYsTEu Fiied Deb. 25. 19:57 'f 3 sheets-sheet 3 Fig. 3.

Inventor:

H R. by #gez/lge Att oT- h ey.

Patented Aug. 1, 1939 PATENT OFFICE 2,1es,1 57 FLUm comme SYSTEM HarryR. Crago, Verona,

eral Electric Company,

York

N. J., assignor to Gena corporation of New Application December 23,1937, Serial No. 181,274

11 Claims.

l to'carry the load need be connected to operate.

In such systems, each machine may be operated more nearly within itsmost eiiicient rangel of load. Accordingly, it is an object of myinvention to provide a fluid cooling system having a plurality ofrefrigerating machines and including an improved arrangement forcontrolling the sequence of operation of the refrigerating machines.

Another object of my invention is to provide a fluid cooling systemhaving a plurality of refrigerating machines and an improved arrangementfor selecting the machines for operation in accordance with the load onthe system.

Further objects and advantages of my inven- -tion will become apparentas the following description proceeds, and the features of novelty whichcharacterize my invention will'be pointed out with particularity in theclaims annexed to and forming' a part of this specification.

' For a better understanding of my invention, reference may be had tothe accompanying drawings in which Fig. 1 is a diagrammatic illustrationof an air cooling system including a refrigerating machine having twocondensing units and embodying my invention; Fig. 2 is a diagrammaticillustration of an air cooling system utilizing two refrigeratingmachines embodying my invention; and Fig. 3 is a diagrammaticillustration of a modified arrangement of an air cooling system similarto that shown in Fig. 2.

Referring now to the drawings, in Fig. 1 I have shown an air coolingsystem including a duct I having a fresh air inlet and a return airinlet |2 provided with nlters I3 and I4 respectively. The fresh andre-circulated air enter the duct and are circulated therethrough byoperation of a fan I5 driven by a motor I5, themixture of air beingdischarged into the room or other enclosure to be conditioned through anoutlet In order to cool the air passing through the duct I0, I provide arefrigerating machine including evaporators I8 and I9 arranged in theduct I9 and connected in a closed refrigerant circuit includingcondensing units and 2| connected in parallel to supply liquidrefrigerant to the evaporators I8 and I9 through a liquid line 22 and towithdraw gaseous refrigerant from the evaporators through a suction line23. The condensing unit 2|! includes a compressor 24, a condenser 25,and a liquid receiver 26. 'I'he condenser is cooled by water circulatedthrough a casing 21' surrounding the condenser and having a coolingwater inlet and an outlet as indicated by the arrows. The condensingunit 2| comprises a compressor 28, a condenser 29, a liquid receiver anda water circulating casing 3| having a cooling Water inlet and an outletas indicatedv by the arrows. The compressors 24 and 28 are driven bymotors 32 and 34 respectively. A'thermostat 35 arranged in the enclosureto be conditioned is tion of the cooling system. When there is a demandfor cooling, one or both of the motors 32 and 34 are operated tocompress refrigerant and discharge the compressed refrigerant into thecorresponding one of the condensers 25 and 29 where the refrigerant iscooled and liquefied by the circulation of Water thereover, the liquidrefrigerant being collected in the receivers 26 and 30. Liquidrefrigerant 'flows through the liquid line 22 and is admitted to theevaporators I8 and I9 by operation of thermostatic expansion valves 36and 3l having thermostatic elements 38 and 39 respectively connected tothe outlet sides of the evaporators. The liquid refrigerant Within theevaporators I8 and I9 absorbs heat from the air circulating through theduct I0 and is vaporized, the vaporized refrigerant being withdrawn andreturnedto the condensing units through the suction line 23. The motorI6 is arranged to drive the fan I5 continuously.

The mixture of air passing through the duct I0 may'vary widely intemperature and relative humidity, and there is, therefore, a widevariation of the load which must be carried by the evaporators. Sinceeach of the condensing units operates most eiliciently within aparticular range of loads for which it is designed, it may be desirableto operate only one of the units when the load is relatively small andto operate both units only when full load is required. It will beevident that if, the condensing units are designed to carry differentloads, it is possible to provide three dif.- ferent ranges of load atwhich the system may operate eiiiciently. For example, if the condensingunit 20 is designed to carry a load of 10 H. P. and the condensing unit2| a load of 20 H. P., it is `possible to operate the system with highefprovided to control the operaciency at loads of 10 H. P., 20 H. P.,and 30 H. P.

,In order to operate the cooling system at maximum eiciency, I providean arrangement for controlling the condensing units and for selectingthe units for operation in accordance with the load demand of thesystem.

, In the arrangement -shown in Fig. 1, whenever there is a. demand forcooling, the thermostat 35 moves to the right and connects a coil 40across the secondary of a transformer 4|, the primary of which isconnected across supply lines 42, and a switch 43 is picked up. 'I'he`upper arm of the switch 43 closes a holding circuit for the coil 40 andthe two lower arms connect leads 44 of the'motor and control circuitacross the lines 42. Motor 32 of condensing unit 20 is thereby connectedto be energized through switches 45 and 46 and a line 41. A coil 48 isalso connected across the lines 44 through a switch 49. The switches 46and 49 are operated by pressure elements 50 and 52 respectively, whichare connected to be responsive to the pressure within the suction line23. The switches 46 'and 49 are pivotally mounted and are operated bythepressure elements 50 and 52 through overcenter springs 46a and 49a.respectively; the switch may, therefore, be set to open at apredetermined low pressure and remain open until-a predetermined higherpressure has been attained. Such pressure operated switches are'commonlyemployed to control refrigerating machines. The coil 48 is arranged topick up an armature 53 of a snap operating mechanism 54 for actuatingswitch 45to connect the moto'r 34 across the lines 44 thorugh a lead 55and the lead 41. It is desirable, however, to preventthe operation ofthe condensing unit 2| which is driven by the motor 34 if the condensingunit 20 can satisfactorily carry the load of the system and I,therefore, provide a time delay device 56 which may be a. dashpot or anyother suitable arrangement for delaying the operation of the switch 45for a predetermined interval of time. If the operation of the condensingunit 20 reduces the pressure within the suction line 23 to apredeterminedV value, say 25pounds per square inch, before the mechanism54 operates to actuate the switch 45, the pressure element 52 'will openthe switch 49 thereby deenergizing the switch 48 and preventing theactuation of the switch 45. Should the continued operation of thecondensing unit 20 reduce the pressure within the suction line 23 to apredetermined minimum, say 29 pounds per square inch, the pressureelement 50 will operate to open the switch 46 and stop the motor 32.Should the condensing unit'20 fail to reduce the pressure within thesuction line 23 sufficiently to open the switch 49, or should thepressure within the suction line 23 rise to a predetermined value, say30 pounds per square inch, after the switch 49 has been openedinitially, the element 52 will close the switch 49.V At

. the end of the interval of time determined by the time delapmechanism56, the plunger 53 will be fully picked up and will actuate the switchmechanism 54 to snap the switch 45 to its upper position `and connectthe motor 34 to operate the condensing unit 2|. The mechanism 54.asillustrated, comprises a pivoted member 51 connected to the switch 45 byan over-center spring 58 to snap the switch between its two extremepositions, it being shown in. its lower position. Whenv the armature 53is fully picked up, a finger 59 engages the member 51 and moves itupwardly so that the overcenter spring snaps the, switch to its upperposition. When the armature 53 drops out, a nger 6| engages the member51 and snaps the switch 45 to its lower position. When the switch 45 isin its upper position, a switch 62 is connected in series in the circuitof the motor 32. The switch 62 is provided with a pressure responsivemember 63 and an overcenter spring 62a which are arranged to open theswitch 62 whenever the pressure in the conduit 23 falls below somepredetermined value, say 30 pounds per square inch. It is, therefore,evident that if the pressure within the conduit 23 is less than 30pounds per square inch when the condensing unit 2| isconne'cted, theswitch '62 will be opened thereby deenergizing the motor 32 and stoppingthe condensing unit 2|l. Under ,this condition of operation, thecondensing unit 2| carries the entire load of the system. Should thepressure within the conduit 23 be greater than 30 pounds per square inchwhen the unit 2| is started, the switch 62 will remain closed. After theswitch 62 has been opened by the pressure element 63, the overcenterspring 62a ysatisied, the thermostat 35 will move to the left toshort-circuit the coil 40 thereby causing the switch 43 to drop out anddisconnect the motors of the condensing units.

During the operation of the cooling system shown in Fig. 1, the motorand control circuits of the condensing units will be energized wheneverthere is a demand for cooling and the pressure elements 52 and '63 willoperate to start and stop the condensing units 20 and 2| in accordancewith the load on the system as determined by the pressure of the gaseousrefrigerant withdrawn from the evaporators I8 and I9. Operation of thesystem at maximum elliciency is thereby assured.

Referring again to the drawings, in Fig. 2 I have shown an air coolingsystem including a duct 64 having a return air inlet 65 and lter.

the mixture of air is returned to the enclosure or room to be cooledthrough a duct 1|. In order to cool the air passing through the duct 64,I provide two refrigerating machines, one comprising an Aevaporator 12and a condensing unit 13 and the other an evaporator 14 and a condensingunit 15. The evaporators 12 and 141 are arranged in the duct 64 so thatthe air is circulated rst over the evaporator 12 and then over theevaporator 14 in series. The condensing unit 13 comprises a compressor16 driven by a motor 11, a condenser 18 and a liquid receiver 19. Thecondenser 18 is cooled by water cir- V culated through a casing havingan inlet and outlet for the water as indicated by the arrows.

`Refrigerant is supplied to the evaporator 12 through a liquid line 8|under control of a thermostatic expansion valve 82 having a thermostaticelement 83 connected in heat exchange relation to the outlet of theevaporator. Gaseous refrigerant is withdrawn from the evaporator througha suction line 84. 'I'he condensing unit,- 15 is similar to thecondensing unit 13 and com- `When there is a demand for'coollng, thethermostat 94 moves to the right and connects a coil 95 across thesecondary of a transformer 96, the primary of which is connected across4the supply lines 91. This energizes the coil 95 and picks up a switch98. The upper arm of the switch closes a holding circuit for the coil 95and the lower arm connects motor and control leads 99 to the supplylines 91 thereby connecting the motors 11 and 86 across the supply linesto start the condensing units 13 and 15. The motor 11 is connectedacross the lines 99 through a line |00, and switches 0| and |02, and themotor 86 is connected across the lines 99 through the line |00 and aswitch |03. 'I'he switches |0l and |03 -are controlled by pressureresponsive members 04 and |05 respectively responsive to the pressuresin the suction lines 84 and 9|, and arranged to operate the switchesthrough overcenter springs |04a and |05a. 'I'hese switches comprise thestandard type of back. pressure control employed on condensing units tostop the operation of the units when a predetermined minimum pressurehas been attained.

If the refrigerating machines are of substantially equal capacity, theevaporator 12 will carry about 60 per cent of the load and theevaporator 14 which is operating in cooled ali` carries about 40 percent of the load. It is readily apparent that under some conditions ofload, one of the evaporators can satisfactorily handle the entire loadof the system. It is, therefore, desirable to provide some arrangementfor cutting out one of the condensing units in the event the load of thesystem is suihciently low to be carried by a single unit. In ordertoaccomplish this purpose, I provide a pressure responsive device |06having an overcenter spring |06a for opening the switch |02 whenever thepressure within the suction line 9|, of the compressor 85 falls below apredetermined value. Opening of the switch |02 opens a circuit of themotor 11 and stops the operation of the condensing unit 13. The entireload then must be carried by the evaporator 14 connected to thecondensing unit 15. In order to prevent the immediate reclosing of theswitch |02 y when the additional. 10aa is added to the evap- 1 12 againbe connected for Service.

unit 13, therefore, is arranged to be operated in ,if which issimilar tothat shown in Fig. 2 and cororator 14, the device |06 is-arranged toreclose the switch at a pressure substantially higher than .that atwhich it operates to open the switch.

'I'he evaporator 14 may, therefore, carry the entire load, and only lfthe load becomes greater than a predetermined value will the evaporatorCondensing accordance with the load on the condensing unlt'16.

Should the demand for cooling be satisiled, the thermostat 94 willengage its left-hand contact and short-circuit the coil 95 therebycausing the switch 98 to drop out and disconnect the motors of therefrigerating machines. l

In Fig. 3, I have shown -an air cooling system responding parts thereofhave been designated by the same numerals. In this arrangement, thecondensing unit 13 which supplies refrigerant to the evaporator 12 isstarted whenever the thermostat 94 calls for cooling and if the load issufliciently low to be carried by one unit, the

condensing unit 1.5 will not be started.` In order to accomplish thisresult, I provide a switch |01 actuated by a pressure responsive device|08 responsive to the pressure in the suction line 84, an overcenterspring |08a being provided to profor delaying the closing of the switchfor a predetermined period after the coil |09 has been energized.v Inthe arrangement illustrated, the device is a dashpot' arranged to delaythe picking up of the switch I0. If the pressure in the suction vline 84is reduced to a predetermined low value before the switch ||0 is closed,the closing of the switch will not start the motor 86 because the device|08 will have operated to open the switch |01. Unnecessary starting ofthe motor 86 is thereby prevented. Should the condensing unit 13 at anytime be unable to carry the load of the system as determined by thesuction pressure in the conduit 84, the switch |01 will be closed andthe motor l86 will be started to drive the 'condensing unit 15 andoperate the evaporator 14 to cool the air in the duct. Operation of thecondensing units 13 and 15 will continue until the demand for cooling issatisfied as determined by the thermostat 94 or until the back pressurein one or both of the suction lines 84 and 9| reaches a predeterminedminimum as determined by the pressure responsive elements |04 and |05.

From the foregoing, it is readily apparent that I have provided a simpleand effective arrangement for dividing the load of a fluid cooling sys--tem between two or more available condensing While I have described myinvention in connection with systems for cooling air, other applicationswill readily be apparent to those skilled in the art, I do not,therefore desire my invention to be. limited to the particularconstructions shown and described and I intend in the appended claims tocover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A fluid cooling system including a refrigerant evaporator, meansincluding two condensing units for supplying refrigerant to saidevaporator and for withdrawing refrigerant from said evaporator, each ofsaid condensing units including means dependent upon a predeterminedpressure of refrigerant Withdrawn from said evaporator for stopping theoperation of said unit, and means dependent upon concurrent operation ofsaid units and responsive to a pressure of said withdrawn refrigerantgreater than the predeter-` mined pressure at which the operation ofeither of said unitsvis stopped by said last-mentioned 'means forstopping the other of said units.

condensing units "for supplying refrigerant to duce a snap action. Whenthe thermostat callsv for coolingand the switch 98 is operated to` 4said evaporator and for withdrawing refrigerant from said evaporator,each of said condensing units including means responsive to the suctionpressure thereof for stopping the operation thereof at a predeterminedlow pressure, and means dependent upon a predetermined pressure of therefrigerant withdrawn from said evaporator and independent of saidlast-mentioned means for stopping the operation of one of saidcondensing units, all of said stopping means cooperating to determinethe sequence of operation of said condensing units.

3. A fluid cooling system including a refrigerant evaporator, meansincluding two condensing units for supplying refrigerant to saidevaporator and for withdrawing refrigerant from said evaporator, meansdependent upon a demand for coolingfor starting one of :aid units, meansdependent upon pressures in excess of a predetermined pressure of therefrigerant withdrawn from said evaporator for starting the other ofsaid units to maintain both of said units in operation, and meansdependent upon concurrent operation of said units and responsive to apressure in excess of said last-mentioned predetermined pressure forstopping the operation of said one of said units. 1

4. A fluid cooling system including a refrigerant evaporator, meansincluding two condensing units of different full load capacities forsupplying refrigerant to said evaporator and for withdrawing refrigerantfrom said evaporator, means dependent upon a demand for'cooling forstarting the one of said units having the lower capacity, meansdependent upon pressures in excess of a predetermined pressure of therefrigerant withdrawn from said evaporator for starting the one of saidunits having the higher capacity to maintain both of said units inoperation, and` means dependent upon operation of said higher capacityunit and responsive to a predetermined pressure of said withdrawnrefrigerant in excess of said lastmentioned predetermined pressure forstopping the operation of said lower capacity unit.

5. A fluid cooling system including a refrigerant evaporator, meansincluding two condensing units for supplying refrigerant to saidevaporator and for withdrawing refrigerant from said evaporator, meansdependent upon a demand for cooling for starting one of said units,means responsive to a predetermined low pressure of said refrigerantwithdrawn from said evaporator for stopping said unit, means dependentupon pressures in excess of a predetermined pressure of the refrigerantwithdrawn from said units for starting the other of said units tomaintain both of said units in operation, means dependent upon operationof both of said units and responsive to a pressure in excess of saidlast-mentioned predetermined pressure for stopping the operation of saidone of said units, and means for delaying the starting of said secondunit for a predetermined interval of time after the pressure of saidwithdrawn refrigerant has reached said predetermined pressure inresponse to which said other of said units is started.

6. A iiuid cooling system including two refrigerating machines, each ofsaid machines having an evaporator, means for circulating a fluid to becooled first over one of said evaporators and then over the other ofsaid evaporators, vmeans for controlling said machines, and meansdependent upon a predetermined load on one of said machines for stoppingthe other of said machines.

7. A fluid cooling system including two refrig- `erating machines, eachof said machines having an evaporator, means for circulating a fluid tobe cooled rst over one of said evaporators and then over the other ofsaid evaporators, means for controlling said machines, means fordelaying the starting of one of saidvmalchines for a predeterminedinterval of time after operation of said controlling means, and meansdependent upon a predetermined load on the other of said machines forstopping said one of said machines.

8. A fluid cooling System including two refrigerating machines, leach ofsaid machines comprising a compressor and a condenser and an evaporator,each of said machines including a pressure operated device for stoppingthe operation of the compressor thereof, means for circulating a fluidto be cooled over said evaporators in series, means for controlling theoperation of said machines, and means responsive to a predeterminedpressure of the refrigerant on the suction side of one of saidcompressors for stopping the operation of the other of said compressors.

9. A fluid cooling system including two refrigerating machines, each ofsaid machines comprising a compressor and a' condenser and anevaporator, means for circulating a fluid t0 be cooled over one of saidevaporators and then over the other of said evaporators, means forcontrolling said machines to supply refrigerant to and withdrawrefrigerant from said evaporators, and means responsive to apredetermined pressure of the refrigerant withdrawn from said other of esaid evaporators for stopping the supply of refrigerant to said one ofsaid evaporators.

10. A fluid cooling system including two refrigerating machines, each ofsaid machines comprising a compressor and a condenser and an evaporator,means for circulating a fluid to be cooled over one of Asaid evaporatorsand then over the other of said evaporators, means for controlling saidmachines to supply refrigerant to and withdraw refrigerant from saidevaporators. and means responsive to a predetermined pressure of therefrigerant withdrawn from said oneof said evaporators for stopping thesupply of refrigerant to said other of said evaporators.

11. 'A fluid cooling system including two refrigerating machines, eachof said machines comprising a compressor and a condenser and anevaporator, means for circulating a fluid to be cooled over one of saidevaporators and then over the other of said evaporators, meansforcentrolling said machines, means for preventing the starting of saidrefrigerating machine including said one evaporator for a predeterminedinterval of time after the starting of said other refrigerating machineby operation of said controlling means, and means repsonsive to apredetermined pressure of the refrigerant withdrawn from said other ofsaid evaporators for stopping the supply of refrigerant to said one ofsaid evaporators.

HARRY R. CRAGO.

